Limited slip differential disassembly method and tool therefor

ABSTRACT

A tool for assembly and disassembly of a limited slip differential including a step plate engageable against one side gear of the differential, an internally-threaded member engageable against the other side gear of the differential, a forcing screw threadable into the threaded member and engageable with the step plate whereby rotation of the forcing screw forces increased separation of the side gears relative to each other by compressing of a Belleville spring between each side gear and the differential case to free the pinion mate gears for inward movement to remove washers associated therewith, and a handle member connected to the internally-threaded member extendable outwardly of the differential case and provided with a pawl engageable with a tooth on a side gear to result in rotation of the engaged side gear and a pair of pinion mate gears of the differential to cause the latter to walk on the other side gear until the pinion mate gears are positioned for removal through openings in the differential case, with the rotation of the handle being about an axis defined by the forcing screw, together with a method of disassembling a limited slip differential by use of a tool as described above.

United States Patent Boers et al.

[451 Mar. 21, 1972 [54] LIMITED SLIP DIFFERENTIAL DISASSEMBLY METHOD ANDTOOL THEREFOR [72] Inventors: Jan H. Boers; Robert C. Rutherford; JohnR. Loquai, all of Owatonna, Minn.

[73] Assignee: Owatonna Tool Company [22] Filed: July 15, 1970 [21]Appl. No.: 54,885

[52] US. Cl. ..29/427, 29/200 D, 29/256,

[51] Int. Cl. ..B23p 19/04, B23b 9/00, B25b 27/00 [58] Field of Search..29/426, 427, 200 D, 256, 258

[56] References Cited UNITED STATES PATENTS 1,980,156 11/1934 Emrick..29/426 X 2,419,473 4/1947 Travilla..... 29/426 X 2,748,454 6/1956Compton 29/426 X 2,872,728 2/1959 Fraser ..29/256 3,012,311 12/1961Shupe ...29/200 3,158,930 12/1964 Wesstrom. ...29/426 X 3,216,09811/1965 Ratz ..29/258 X Primary Examiner-Wayne A. Morse, Jr.Attorney-Hofgren, Wegner, Allen, Stellman & McCord [5 7] ABSTRACT A toolfor assembly and disassembly of a limited slip differential including astep plate engageable against one side gear of the'differential, aninternally-threaded member engageable against the other side gear of thedifferential, a forcing screw threadable into the threaded member andengageable with the step plate whereby rotation of the forcing screwforces increased separation of the side gears relative to each other bycompressing of a Belleville spring between each side gear and thedifferential case to free the pinion mate gears for inward movement toremove washers associated therewith, and a handle member connected tothe internally-threaded member extendable outwardly of the difierentialcase and provided with a pawl engageable with a tooth on a side gear toresult in rotation of the engaged side gear and a pair of pinion mategears of the differential to cause the latter to walk on the other sidegear until the pinion mate gears are positioned for removal throughopenings in the differential case, with the rotation of the handle beingabout an axis defined by the forcing screw, together with a method ofdisassembling a limited slip differential by use of a tool as describedabove.

14 Claims, 4 Drawing Figures LIMITED SLIP DIFFERENTIAL DISASSEMBLYMETHOD AND TOOL THEREFOR BACKGROUND OF THE INVENTION This inventionpertains to a tool for assembly and disassembly of a limited slipdifferential and to the method of disassembling such a differential.

SUMMARY An object of the invention is to provide a new and improved toolfor assembly and disassembly of a limited slip differential wherein theside gears of the differential each has a clutch pack and Bellevillespring associated therewith whereby the tool compresses the springs tofacilitate removal of washers associated with the pair of pinion mategears and wherein the structure for compressing said springs furtherdefines an axis of rotation for a handle carrying a gear rotating toolor element which advances one of the side gears and the pinion mategears to positions for removal of the pinion mate gears and otherstructure from the differential case.

Still another object of the invention is to provide a tool for assemblyand disassembly of a limited slip differential having a step platefittable into the central axle-receiving opening of one side gear of thedifferential, an internally threaded nut fittable into theaxle-receiving opening of the other side gear and with an elongatehandle connected thereto for extension outwardly of the differentialcase, a forcing screw positionable in the differential case and in theinternally threaded nut whereby rotation of the forcing screw will exertforces in opposing relation against the pair of side gears to compressBelleville springs associated with each of the side gears to free thepinion mate gears for inward movement to permit removal of washersassociated therewith, and a pawl positionable on the handle to engage atooth on one side gear whereby rotation of the handle about an axisdefined by the forcing screw causes rotation of the last-mentioned sidegear and pinion mate gears until the latter gears are walked topositions to permit removal through openings in the differential case.

Still another object of the invention is to provide a method ofdisassembly of a limited slip differential having a pair of spaced-apartside gears meshing with a pair of pinion mate gears and with a clutchpack and Belleville spring between each side gear and the differentialcase comprising, removal of a cross pin passing through the pinion mategears, positioning elements between opposing faces of said side gearsand actuating said element to exert forces in directions to urge saidside gears apart and compress the Belleville springs whereby the pinionmate gears can move inwardly to permit removal of spherical washersbetween the differential case and said pinion mate gears, substantiallyreleasing said forces, holding one side gear against rotation, androtating the other side gear by a member connected to one of saidelements to rotate said pinion mate gears and walk the latter on saidone side gear until the pinion mate gears are positioned for removalthrough openings in the differential case, followed by removal of saidside gears and associated structure from the differential case.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical central section ofa limited slip differential with the ring gear removed and mounted on anaxle positioned in a vise;

FIG. 2 is a view, similar to FIG. 1, showing the limited slipdifferential with the tool structure associated therewith;

FIG. 3 is a vertical assembly view of the tool; and

FIG. 4 is a perspective of the limited slip differential and tool.

DESCRIPTION OF THE PREFERRED EMBODIMENT The limited slip differentialdisclosed herein has recently come on the market and the specificstructure disclosed is that offered by Dana Corporation under itstrademark TRAC- LOK. A conventional differential transmits all of thering gear torque through the differential gears to the axle shafts. Thelimited slip differential difiers from the conventional differential inthat part of the torque from the ring gear is transmitted through clutchpacks between the side gears and the differential case. These clutchpacks include disc clutches with radial grooves on the plates andconcentric grooves on the discs which are engaged by a preload fromBelleville springs plus separating forces from the side gears as torqueis applied through the ring gear. This construction permits differentialaction when required for turning corners and transmits equal torque toboth wheels when driving straight ahead. When one wheel tries to spin,due to leaving the ground, the clutch packs automatically provide moretorque to the wheel which is not trying to spin.

More specifically, the limited slip differential embodies a difierentialcase 10 having opposed axle-receiving openings 11 and 12 communicatingwith an interior chamber 15. An annular flange 16 has bolt-receivingopenings 17 to which a ring gear (not shown) may be attached. The wallof the differential case 10 has a pair of side openings, one of which isshown at 20, of substantial peripheral dimension and a pair ofpinreceiving openings 22 and 23 to receive a cross pin 24. A pair ofside gears 25 and 26 are positioned within the differential casechamber, with each of these gears having splined axlereceiving openings27 and 28, respectively. The splined opening 27 of the top side gear 25,as shown in FIG. 1, normally receives the inner end of one axle, whilethe splined opening 28 of the bottom side gear 26 receives the splinedend of the other axle. Each side gear has a clutch pack and Bellevillespring associated therewith. The top side gear 25 has the Bellevillespring 30 engaging a flat surface on the side gear and a portion of theclutch pack with the clutch pack including plates and discs, indicatedgenerally at 31, with the discs being splined to an exterior spline onthe side gear. A similar clutch pack and Belleville spring areassociated with the bottom side gear 26, with the spring identified at35 and the clutch pack identified generally at 36. The side gears eachhave a series of teeth 40 and 41, respectively, which mesh with a pairof pinion mate gears 45 and 46 rotatable on the cross pin 24. The mategears 45 and 46 are held in position by a pair of removable snap rings47 and 48 and with the outer surfaces thereof spaced from thedifferential case 10 by spherical washers 49 and 50 having centralopenings through which the cross pin 24 extends.

In order to disassemble the limited slip differential, the unit ismounted, as shown in FIGS. 1 and 2, with an axle A mounted in a vise orsimilar holding device 60 and with only a limited amount of the splinedend of the axle extending thereabove, whereby the differential case willbe positioned with a portion of the axle-receiving opening 28 open.

The first step in disassembly is to remove the snap rings 47 and 48manually by use of a screw driver or the like inserted through a sideopening of the differential case, followed by knock-out of the crosspin.

The tool embodying the invention is then utilized in the subsequentdisassembly steps. This tool embodies a step plate 70 having aconcentric plug portion 71 which fits into the axlereceiving opening 28of the bottom side gear 26 and with the step plate resting on the faceof the side gear. Additionally, the step plate has a pilot recess 72. Asecond part of the tool comprises a circular member having an internallythreaded opening to, in effect, define a forcing nut 75. The forcing nut75 has a concentric plug portion 75a to fit into the axle-receivingopening 27 of the side gear 25. This nut has an elongate handle 76attached thereto and of a length to extend out through one of the sideopenings in the differential case 10 and with a gripping portion 77. Aforcing screw 80 has a threaded part 81 which engages in the threads ofthe forcing nut 75 and'an upper multisided part for engagement by awrench.

With the parts of the tool thus described, the next step after removalof the cross pin is to insert the step plate 70 into position, as shownin FIG. 2. By manually gripping the handle portion 77, the forcing nutis placed with its concentric plug portion 75a in the axle-receivingopening 27 of the side gear 25. The forcing screw 80 is then insertedthrough the axle-receiving opening 11 of the case and the axle-receivingopening 27 of the side gear 25 and the threads on the part 80 broughtinto threaded engagement with the forcing nut. Rotation of the forcingscrew then brings a pilot 82 at the lower end of the forcing screw intothe pilot recess 72. This holds the forcing screw firmly in position.Added rotation of the forcing screw then exerts forces on the side gearsto urge them further apart and compress the Belleville springs 30 and35. This increased space between the side gears permits the pinion mategears 45 and 46 to move inwardly sufficient to free the sphericalwashers 49 and 50 whereby they may be pushed out from behind the pinionmate gears for removal from the case.

The forcing screw is them backed off to reduce the compression of theBelleville springs but still to maintain the forcing screw and stepplate in firm engagement, since the forcing screw forms a rotation axisfor the handle in the manner to be described.

The tool further includes a gear tooth engaging pawl 90 movably mountedon the handle 76 to and from a detented position defined by a notch 91in the handle. In this detented position, the pawl 90 is positioned forengagement with a tooth on the top side gear 25. With this engagement,and upon rotation of the handle 76 along with resultant rotation of theforcing nut 75, the top side gear is caused to rotate. At this time, thebottom side gear 26 is held against rotation by its splined engagementwith the axle which is locked in the vise. This rotation of the top sidegear also causes rotation of the pinion mate gears 45 and 46 which thuswalk along the bottom side gear 26. The are of movement of the handle 76is limited and more than one stroke of the handle may be required;thereby, the pawl 90 can be moved outward from its detented position topermit the handle to swing back to an initial position and the pawl thenmoved back into detented position for another stroke of the handle. Thisis repeated a sufficient number of times until the pinion mate gears aremoved into alignment with the side openings for removal from thedifferential case. Following removal of the pinion mate gears then theside gears and clutch packs can be removed.

From the foregoing, it will be seen that a method of disassembling alimited slip differential is provided wherein the steps include removalof the cross pin followed by positioning elements between opposing facesof the side gears and 26 and actuating the elements, namely, the forcingscrew, to exert forces urging the side gears apart and to compress theBelleville springs whereby the spherical washers behind the pinion mategears can be removed. The forces are substantially released and one sidegear is held against rotation whereby rotating the other side gear bythe pawl carried on the rotatable handle rotates the pinion mate gearsand the side gear to walk the pinion mate gears to a position where theycan be removed.

The assembly of the limited slip differential follows the reverse of theprocedure set forth for disassembly and it is believed that such stepsare readily understood without detailed recitation thereof.

From the foregoing it will be seen that a tool has been provided whichenables internal positioning of tool components within the differentialcase to separate the side gears sufficiently to permit removal of thewashers associated with pinion mate gears and with this structurefurther defining a rotational axis for a handle carrying a pawl forrotating a side gear and the pinion mate gears to a removal position.

We claim:

1. A tool for assembly and disassembly of a limited slip differentialhaving a pair of spaced-apart side gears meshing with a pair of pinionmate gears and with a clutch pack and Belleville spring between eachside gear and the differential case comprising, a plate fittable againstone side gear, an internally threaded nut fittable against the otherside gear and having an elongate handle connected thereto for extensionoutwardly of the differential case, a forcing screw extendable throughsaid nut and rotatably advanceable into interfitting engagement with thestep plate with further rotation increasing the spacing between the sidegears by compression of the Belleville springs to free the pinion mategears for inward movement to remove washers associated therewith, and apawl on said handle for engagement with a tooth on a side gear wherebyrotation of said handle about an axis defined by the forcing screwcauses rotation of the last-mentioned side gear and pinion mate gearsuntil the pinion mate gears are walked to a position to permit removalthrough openings in the differential case.

2. A tool as defined in claim 1 wherein said pawl is movable relative tosaid handle to move into and out of engagement with a side gear tooth.

3. A tool as defined in claim 2 wherein said pawl is movable lengthwiseof said handle, and coacting structure on the pawl and handle to holdthe pawl in engagement with a side gear tooth.

4. An assembly and disassembly tool for a limited slip differentialcomprising, a step plate engageable with one side gear of said limitedslip differential, an internally threaded member engageable with theother side gear of said limited slip differential, a forcing screwthreadable into said member and engageable with the step plate wherebyrotation of said forcing screw will force said side gears a furtherdistance apart, a handle having a gear tooth engaging pawl adjustablypositionable thereon for engaging a tooth of a side gear to causerotation thereof as the handle is rotated about a central axis of thedifferential.

5. An assembly and disassembly tool for a limited slip differentialcomprising, a step plate engageable with one side gear of said limitedslip differential, an internally threaded nut engageable with the otherside gear of said limited slip differential, a forcing screw threadableinto said nut and engageable with the step plate whereby rotation ofsaid forcing screw forces said side gears a further distance apart, ahandle extending from said nut, and a gear tooth engaging pawladjustably positionable on the handle for engaging a tooth of a sidegear to cause rotation thereof as the handle is rotated about an axisdefined by the forcing screw.

6. A tool as defined in claim 5 wherein said step plate and forcing nuteach has a concentric plug section to fit into the axle-receivingopenings of their adjacent side gears.

7. A tool as defined in claim 5 wherein said step plate has a centralpilot recess and said forcing screw has a conical pilot end engageablein said recess to hold the forcing screw in position during rotation ofsaid handle and forcing nut about said forcing screw.

8. A tool as defined in claim 5 wherein said pawl is movable along saidhandle and the handle has detent means engageable with the pawl to holdthe pawl in proper position when the pawl engages the side gear tooth. I

9. A tool for assembly and disassembly of a limited slip differentialhaving a pair of spaced-apart side gears meshing with a pair of pinionmate gears and with a clutch pack and Belleville spring between eachside gear and the differential case comprising, a step plate fittableinto the central axle-receiving opening of one side gear, an internallythreaded nut fittable into the axle-receiving opening of the other sidegear and having an elongate handle connected thereto for extensionoutwardly of the differential case, a forcing screw extendable throughan end of said differential case and said nut and rotatably advanceableinto interfitting engagement with the step plate with further rotationincreasing the spacing between the side gears by compression of theBelleville springs to free the pinion mate gears for inward movement toremove washers associated therewith, and a pawl movable on said handleto a position to engage a tooth on a side gear whereby rotation of saidhandle about an axis defined by the forcing screw causes rotation of thelast-mentioned side gear and pinion mate gears until the pinion mategears are walked to positions to permit removal through openings in thedifferential case, said forcing screw having been backed off sufficientto relieve the compression on the Belleville springs but still in firmengagement with the step plate.

10. A tool as defined in claim 9 wherein said handle has detent meansengageable with the pawl to hold the pawl in proper position on thehandle when the pawl engages the side gear tooth.

11. A tool as defined in claim 9 wherein said step plate has a centralpilot recess and said forcing screw has a conical pilot end engageablein said recess to hold the forcing screw in position during rotation ofsaid handle.

12. A tool as defined in claim 9 wherein said step plate and forcing nuteach has a concentric plug section to fit into the axle-receivingopenings of their adjacent side gears.

13. A method for disassembly of a limited slip differential having apair of spaced-apart side gears meshing with a pair of pinion mate gearsand with a clutch pack and Belleville spring between each side gear andthe differential case comprising, removing a cross pin passing centrallythrough the pinion mate gears, exerting forces on opposing faces of saidside gears in directions to urge said side gears apart and compress theBelleville springs whereby the pinion mate gears can move inwardly topermit removal of spherical washers against and walk the latter on saidone side gear until the pinion mate gears are positioned for removalbetween the differential case and said pinion mate gears, releasing saidforces, holding one side gear against rotation, and rotating the otherside gear to rotate said pinion mate gears and walk the latter on saidone side gear until the pinion mate gears are positioned for removalthrough openings in the differential case, followed by removal of saidside gears and associated structure from the differential case.

14. A method for disassembly of a limited slip differential having apair of spaced-apart side gears meshing with a pair of pinion mate gearsand with a clutch pack and Belleville spring between each side gear andthe differential case comprising, removal of a cross pin passing throughthe pinion mate gears, positioning elements between opposing faces ofsaid side gears and actuating said elements to exert forces indirections to urge said side gears apart and compress the Bellevillesprings whereby the pinion mate gears can move inwardly to permitremoval of spherical washers between the difierential case and saidpinion mate gears, substantially releasing said forces, holding one sidegear again rotation, and rotating the other side 'gear by a memberconnected to one of said elements to rotate said pinion mate gears arepositioned for removal through openings in the differential case,followed by removal of said side gears and associated structure from thedifferential case.

1. A tool for assembly and disassembly of a limited slip differential having a pair of spaced-apart side gears meshing with a pair of pinion mate gears and with a clutch pack and Belleville spring between each side gear and the differential case comprising, a plate fittable against one side gear, an internally threaded nut fittable against the other side gear and having an elongate handle connected thereto for extension outwardly of the differential case, a forcing screw extendable through said nut and rotatably advanceable into interfitting engagement with the step plate with further rotation increasing the spacing between the side gears by compression of the Belleville springs to free the pinion mate gears for inward movement to remove washers associated therewith, and a pawl on said handle for engagement with a tooth on a side gear whereby rotation of said handle about an axis defined by the forcing screw causes rotation of the last-mentioned side gear and pinion mate gears until the pinion mate gears are walked to a position to permit removal through openings in the differential case.
 2. A tool as defined in claim 1 wherein said pawl is movable relative to said handle to move into and out of engagement with a side gear tooth.
 3. A tool as defined in claim 2 wherein said pawl is movable lengthwise of said handle, and coacting structure on the pawl and handle to hold the pawl in engagement with a side gear tooth.
 4. An assembly and disassembly tool for a limited slip differential comprising, a step plate engageable with one side gear of said limited slip differential, an internally threaded member engageable with the other side gear of said limited slip differential, a forcing screw threadable into said member and engageable with the step plate whereby rotation of said forcing screw will force said side gears a further distance apart, a handle having a gear tooth engaging pawl adjustably positionable thereon for engaging a tooth of a side gear to cause rotation thereof as the handle is rotated about a central axis of the differential.
 5. An assembly and dIsassembly tool for a limited slip differential comprising, a step plate engageable with one side gear of said limited slip differential, an internally threaded nut engageable with the other side gear of said limited slip differential, a forcing screw threadable into said nut and engageable with the step plate whereby rotation of said forcing screw forces said side gears a further distance apart, a handle extending from said nut, and a gear tooth engaging pawl adjustably positionable on the handle for engaging a tooth of a side gear to cause rotation thereof as the handle is rotated about an axis defined by the forcing screw.
 6. A tool as defined in claim 5 wherein said step plate and forcing nut each has a concentric plug section to fit into the axle-receiving openings of their adjacent side gears.
 7. A tool as defined in claim 5 wherein said step plate has a central pilot recess and said forcing screw has a conical pilot end engageable in said recess to hold the forcing screw in position during rotation of said handle and forcing nut about said forcing screw.
 8. A tool as defined in claim 5 wherein said pawl is movable along said handle and the handle has detent means engageable with the pawl to hold the pawl in proper position when the pawl engages the side gear tooth.
 9. A tool for assembly and disassembly of a limited slip differential having a pair of spaced-apart side gears meshing with a pair of pinion mate gears and with a clutch pack and Belleville spring between each side gear and the differential case comprising, a step plate fittable into the central axle-receiving opening of one side gear, an internally threaded nut fittable into the axle-receiving opening of the other side gear and having an elongate handle connected thereto for extension outwardly of the differential case, a forcing screw extendable through an end of said differential case and said nut and rotatably advanceable into interfitting engagement with the step plate with further rotation increasing the spacing between the side gears by compression of the Belleville springs to free the pinion mate gears for inward movement to remove washers associated therewith, and a pawl movable on said handle to a position to engage a tooth on a side gear whereby rotation of said handle about an axis defined by the forcing screw causes rotation of the last-mentioned side gear and pinion mate gears until the pinion mate gears are walked to positions to permit removal through openings in the differential case, said forcing screw having been backed off sufficient to relieve the compression on the Belleville springs but still in firm engagement with the step plate.
 10. A tool as defined in claim 9 wherein said handle has detent means engageable with the pawl to hold the pawl in proper position on the handle when the pawl engages the side gear tooth.
 11. A tool as defined in claim 9 wherein said step plate has a central pilot recess and said forcing screw has a conical pilot end engageable in said recess to hold the forcing screw in position during rotation of said handle.
 12. A tool as defined in claim 9 wherein said step plate and forcing nut each has a concentric plug section to fit into the axle-receiving openings of their adjacent side gears.
 13. A method for disassembly of a limited slip differential having a pair of spaced-apart side gears meshing with a pair of pinion mate gears and with a clutch pack and Belleville spring between each side gear and the differential case comprising, removing a cross pin passing centrally through the pinion mate gears, exerting forces on opposing faces of said side gears in directions to urge said side gears apart and compress the Belleville springs whereby the pinion mate gears can move inwardly to permit removal of spherical washers against and walk the latter on said one side gear until the pinion mate gears are positioned for removal between the differential case and said pinion mate gears, releasing said forces, holding one side gear againSt rotation, and rotating the other side gear to rotate said pinion mate gears and walk the latter on said one side gear until the pinion mate gears are positioned for removal through openings in the differential case, followed by removal of said side gears and associated structure from the differential case.
 14. A method for disassembly of a limited slip differential having a pair of spaced-apart side gears meshing with a pair of pinion mate gears and with a clutch pack and Belleville spring between each side gear and the differential case comprising, removal of a cross pin passing through the pinion mate gears, positioning elements between opposing faces of said side gears and actuating said elements to exert forces in directions to urge said side gears apart and compress the Belleville springs whereby the pinion mate gears can move inwardly to permit removal of spherical washers between the differential case and said pinion mate gears, substantially releasing said forces, holding one side gear again rotation, and rotating the other side gear by a member connected to one of said elements to rotate said pinion mate gears are positioned for removal through openings in the differential case, followed by removal of said side gears and associated structure from the differential case. 